Antenna feeding system



Dec. 28, 1965 L- R. WHITE ANTENNA FEEDING SYSTEM 2 Sheets-Sheet 1 Filed March 11, 1949 INVENTOR. LEE R. WHITE ATTORNEY Dec. 28, 1965 L. R. WHITE ANTENNA FEEDING SYSTEM 2 Sheets-Sheet 2 Filed March 11, 1949 INVENTOR. LEE R. WH ITE ATTORNEY United States Patent 3,226,723 M ANTENNA FEEDING SYSTEM Lee R. White, 2118 University Ave, Madison, Wis. Filed Mar. 11, 1949, Set. No. 80,982 6 Claims. (Cl. 343- -852) (Granted under Title 35, US. Code (1952), sec. 266) This invention relates to a coupling system for the transfer of radio frequency energy. While not limited thereto, the invention is particularly useful in the simultaneous transmission or reception of a plurality of signals of different frequencies with asingle antenna.

In the past it has been customary to provide each radio frequency translating device (e.g., transmitter and receiver) with a separate antenna. However, the use of radio wave energy has been extended to so many different purposes and the number of units for each purpose has been so increased that in many places it has become physically impossible to provide a separate antenna for each equipment. For example, on shipboard installations thare are a limited number of possible antenna locations which permit desirable directional characteristics. It has, therefore, become necessary to employ one antenna for a plurality of equipments. The use of a single antenna for a plurality of translating devices also has the obvious advantage of economy.

For maximum effectiveness at the higher frequencies, the physical dimensions of an antenna should be properly related with the wavelength of the energy thereon. A single antenna, however, may be suitable for use at any one of a band of frequencies. It is therefore an object of this invention to provide means for coupling a plurality of simultaneously operable transmitters or receivers to a single antenna, the transmitters or receivers being tuned to different frequencies.

It is another object to provide means for coupling differently tuned transmitters or receivers to a common antenna without interference by one transmitter or receiver with another.

It is a further object to provide means for coupling a wave translating device to an antenna in such a manner as to maximize the transfer of energy.

It is a further object to provide coupling means between a wave translating device and an antenna,- the coupling device being physically adjustable to present a low impedance to the transfer of energy having the frequency of the translating device and a high impedance to energy of other frequencies.

In pursuance of these and other objects which will be apparent to those skilled in the art, there is provided a coaxial transmission line which is shorted at one end and connected to a load, e.g., an antenna, at the other end. A plurality of wave translating devices are each coupled through an adjustable quarter wave element to a different portion of the transmitter line. The distance of each quarter wave coupling element from the shorted end of the line is adjustable by suitable means, independently and without altering the distance of the remaining coupling elements from the shorted end of the line, to provide optimum transfer of energy between the corresponding wave translating device and the line. When the apparatus is properly tuned, in a manner to be described hereinafter, the plurality of translating devices are simultaneously operable at ditferent frequencies with a single antenna. I

A better understanding of the invention may be obtained from the following description of one embodiment taken with the appended .drawings wherein:

FIGURE 1 is a coupling system connecting two translating devices and a single antenna.

FIGURE 2 is a perspective View of a single coupling device, parts being broken away to illustrate internal details.

FIGURE 3 is afragmentary plan view of a part of the coupling device illustrating details of construction.

FIGURE 4 is an elevational view of the same.

Referring now in greater detail to the drawings, and in particular to FIG. 1 the invention is shown as applied to a single antenna 10 coupled to a plurality of wave translating devices 11 and 12. The antenna 10 is connected to one end 13 of a coaxial line the other end 14 of which is shorted. The coaxial line section 15, having a solid dielectric, connecting the antenna 10 to a larger SO-ohm coaxial line unit, generally designated 16, having an air dielectric. The other end of unit 16 is connected by a conventional 50ohm coaxial line 17 to a second coaxial line unit generally designated 18 which is similar to unit 16. The other end 14 of unit 18 is shorted.

The coaxial line units 16 or 18 include enlarged stationary end sections 20 and 21 provided with conventional tapered transition sections 22 and 23 for connection with coaxial lines 15 and 17. An intermediate tubular section generally designated 25 of the coaxial line unit 16 is telescopically engaged with the end sections 20 and 21, thereby permitting longitudinal displacement of the intermediate section 25 along the line unit 16. It is to be understood that both the inner and outer conductors of the enlarged section 25 are telescopically en'- gaged with the inner and outer conductors, respectively, of the end sections 20 and 21.

An intermediate portion 26 of the outer conductor of line section 25 is enlarged to provide a coupling cavity. In FIG. 1 and also in the perspective view of FIG. 2, the enlarged portion 26 is shown as a metallic rectangular box 27 constructed around the outer conductor of line section 25. A semi-cylindrical portion of the part of the outer conductor of line section 25 within the box 27 is cut away leaving a semi-cylindrical shell 28. The lower wall 29 of box 27 extends tangentially from the lower edge of the shell 28.

p A coupling element 30 is disposed in the box 27 adjacent the exposed side of the inner conductor 31 of line section 25 and in parallel relation with the conductor 31 and the wall 29. One end of the main portion 32 of the coupling element 30 is electrically connected with the wall 29 of box 27 by a post 33 of conductive material. The other end is securely supported by a post 34 of insulating material. An extensible portion 35 of the coupling element 30 is telescopically engaged with the main portion 32 to permit adjustment of the effective electrical length of the coupling element. Normally, the coupling element 30 will be adjusted in length to approximately one-fourth the wavelength of the energy to be coupled. An adjusting extension rod 36 of an insulating material is connected to one end of the extensible portion 35, the other end of rod36 extends outside the box 27 and is provided with a hand knob 37. calibrations 38 on the rod 36 are provided for reading against the edge 39 of the box 27 or any suitable pointer.

The wave translating device 12 is connected to the coupling element 30; by means of a flexible coaxial line 42, an air filled coaxial coupling line 43 which extends through the side wall 44 of box 27 into the interior thereof, and a strap 45. As shown to advantage in FIGURES 3 and 4, the coupling line 43 is disposed with it outer conductor 46 adjacent to the bottom wall 29 of box 27. The end of the outer conductor 46 is beveled and the inner conductor 47 is slotted to receive the conductive strap 45. The strap 45 is appropriately formed to make contact with the post 33 at a short distance D from the Wall 29 of box 27 The entire intermediate conductor section 25 of the co axial line unit 16 is longitudinally adjustable in position rod 50 journaled in brackets 51 and 52. h A nut '53 isin' threaded engagement with the screw rod 50 and is fixed to the intermediate section 25 of the unit 16. A crank handle 54 permits manual adjustment of the position of intermediate section 25 without changing the lengthof the coaxial line unit 16. Calibrations 55 on the end section 21 may be read against the edge 56 of the intermediate section 25.

Coaxial line unit 18, for wave translating device 11, is the same in construction a coaxial line unit 16. It is to be understood than any reasonable number of coaxial line units may be interposed between antenna 16 and short circuit 14. It will be noted that the" adjustment of the position of the intermediate iline section 25 of unit 18 does not alter the distance of intermediate line section 25 of unit 16 from the shorted end 14 of the composite line. Since each coupling element is fixed to its corresponding intermediate line section, the construction shown permits the independent adjustment of the distance of any one of a plurality of coupling elements from the shorted end 14 of the composite line without disturbing the corresponding distance of the other coupling elements. The

distance of a coupling element from the shorted end of the line in terms of wavelength affects the degree of energy transfer between the element and the antenna. The positions of maximum energy transfer for any one frequency are about one-half wavelength apart along the line.

Each coupling element 30 is normally adjusted in length to substantially one-quarter wavelength at the frequency of the corresponding Wave translating device. There is a high impedance to the coupling of energy of any other frequency than that to which the coupling element is tuned. Therefore, energy of several different frequencies may be simultaneously present-on the line and energy of each frequency will be coupled by a correspondingly tuned coupling element substantially as though there were no other energy or coupling elements on the line.

tion ha been shown and described in some detail, it will be understood-that modifications "and" changes" as'will A system constructed in accordance with the teaching of this invention for use with four translating devices simultaneously oeprable in the range of frequency'values from 200 to 400 megacycles functioned satisfactorily and will be described. Conventional SO-ohm coaxial transmission lines 15 and 17 were connected to 50-ohm air dielectric transmission lines 20 and 21 having an outside diameter of 1% inches. The rectangular metal box l7 was 18 x 5 x 4 /2 inches in size. The two telescoping sections between which the rectangular metal box is located was capable of moving 16 inches; thus a total change of 26 inches in the line length or one-half wavelength at 230 megacycles is possible on each ide. intermediate line section was of sufiicient length on either side of box 27 to cover the entire exposed section of inner conductor 31 at either extreme position of adjustment and to still maintain permissible maximum adjustment.

The optimumspacing between the centers of the inner conductor 31 and the coupling element 30 was found to be 1 /2 inches in this frequency range. The center line of the coupler 30 was 7 inches above wall 29 'of'box 2-7. In order that the composite line have a continuous 50-ohm impedance from the antenna 10 to the shorted end 14, the diameter of the exposed portion eithe -inner conductor 31 within the box 27 is preferably increased.

The strap 45 was connected to the coupler post-'33 at a distance D of about W of an inch from the wall-29 of box 27. 'While it might be desirable tohave-the dimension D adjustable, it was found not to be necessary. Decreasing the dimension "D decreased the range of frequencies of energy that would be" transferred between'the coupling element 30 and the linefand increased the criticalness of adjustment. It was determined that'- a plurality of signals having a frequency separat-ion'of'5 percent or more could be simultaneously present in'the'system without-interfering with each other.

t While a presently'preferred embodiment of the -invenbe known to those skilled in'the art may be made without departing from the spirit of the invention as defined in the claims.

The invention-described herein, may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is: a!

1. A system for coupling a plurality of radio wave translating devices which are tuned to different frequencies to a single antenna,"comprising: a coaxial line shorted at one end and connected to the antenna at the other end, the outer conductor of said line including a plurality of enlarged sections forming a like member of cavities through which the inner conductor of said line passes, a quarter wave couplingelement for each translating device in a corresponding one of said en larged sections and in electrical coupled relation to said inner conductor, means for adjusting the length of each coupling element and means for adjusting thedistance of each coupling element from the shorted end of the line.

2. A system for simultaneously coupling a plurality of wave translating devices of different frequencies'to a single antenna, comprising: a coaxial transmission line shorted at one end and connected to the'antenna at the other end and including a plurality of intermediate telescoping sections adjustable in distance from the shorted end of the line without changing-the total length-of the line, a part of the outer conductor" of each intermediate telescoping section being enlarged, a coupling element therein parallel with the inner conductor and connected at one end to the enlarged outer conductor, and separate connecting means between each translating device and a point on *its corresponding coupling element.

3. In a system for coupling a wave-translating device to an antenna, a coaxial line having a semi-cylindrical portion of the outer conductorcut away exposing the inner conductor, a conductive sheet extending tangentially from one cut edge of the outer conductor, a quarterw'avelength coupling elementeonnected at one end to the conductive sheet and extending in parallel spaced relationship with the conductive sheetand the exposed inner conductor, and a connector between the translating device and a point on the coupling element. 4

4. In a system for coupling a wave translating device to an antenna, a coaxial transmission line shorted at one end, the coaxial line including end portions and an intermediate portion telescopically engaged therewith, crank means for varying the position of the intermediate portion of the line relative to the .shorted end without changing the total length of-the line, a part of the outer conductor of the'intermediate po'rtionof the line being enlarged, a coupling element therein parallel with the inner conductor and connected at one end to the outer conductor, and connecting means between the translating device and a point on the coupling element.

5. A system for simultaneously coupling a plurality of electrical devices operative at different frequencies to an antenna comprising a coaxial line having a given predetermined length, means coupling saidantenna to one end of said line, said line includinga plurality of intermediate portions having an. enlarged outer conductor, a respective coupling element comprising a resonant length conductor and located in the cavity enclosed by each of said enlarged portions parallel to and in electrical coupled relation to the inner conductor of said coaxial line, means electrically connecting each of said electrical devices to a respective coupling element, means for saparately moving each enlarged coaxial line portions and the coupling "elements therein relative to one end of the line without changing the overall length thereof.

6. A system for simultaneously coupling a plurality of electrical devices operative at different frequencies to an antenna comprising a coaxial transmission line including a plurality of separated intermediate telescoping sections separately adjustable in distance from one end of said line without changing the overall length thereof, means connecting said antenna to one end of said coaxial line, each of said telescoping sections including a portion having an enlarged outer conductor, respective coupling elements resonant to a different frequency located in the cavity enclosed by each of said enlarged portions in electrical coupled relation to the inner conductor of said coaxial line, means electrically connecting each of said electrical devices to a different one of said coupling elements.

References Cited by the Examiner UNITED STATES PATENTS 2,259,510 10/1941 Alford 178-44.1 2,412,393 12/1946 Ghosh 17195.23 2,454,042 11/1948 Dettinger 171-9523 2,523,254 9/1950 Talpey 17844.1 2,531,777 11/1950 Marshall 178-441 2,584,272 2/1952 Keizer et a1 17844.1

10 ELI LIEBERMAN, Acting Primary Examiner.

DAVID J. GALVIN, JAMES L. BREWRINK, NOR- MAN H. EVANS, Examiners.

G. S. BLACK, F. M. STRADLER, A. D. MESSENHEIM- ER, Assistant Examiners. 

1. A SYSTEM FOR COUPLING A PLURALITY OF RADIO WAVE TRANSLATING DEVICES ARE TUNED TO DIFFERENT FREQUENCIES TO A SINGLE ANTENNA, COMPRISING: A COAXIAL LINE SHORTED AT ONE END AND CONNECTED TO THE ANTENNA AT THE OTHER END, THE OUTER CONDUCTOR OF SID LINE INCLUDING A PLURALITY OF ENLARGED SECTIONS FROMING A LIKE MEMBER OF CAVITIES THROUGH WHICH THE INNER CONDUCTOR OF SAID LINE PASSES, A QUARTER WAVE COUPLING ELEMENT FOR EACH TRANSLATING DEVICE A CORRESPONDING ONE OF SAID ENLARGED SECTIONS AND IN ELECTRICAL COUPLED RELATION TO SAID INNER CONDUCTOR, MEANS FOR ADJUSTING THE LENGHT OF EACH COUPLING ELEMENT AND MEANS FOR ADJUSTING THE DISTANCE OF EACH COUPLING ELEMENT FROM THE SHORTED END OF THE LINE. 